Dry stress-induced phosphorylation of Physarum actin.
Protein phosphorylation plays important roles in a variety of stress responses. Although plasmodium of Physarum polycephalum rapidly grows and shows an active cytoplasmic streaming under nutrient and wet conditions, dry stress transforms plasmodium into a dormant state called sclerotium. Sclerotium can change into plasmodium within several hours after addition of water. We herein report that more than half of actin in sclerotium was in a phosphorylated state. The in vivo phosphorylation site was identified to be Thr-203 which is in contact with another actin molecule upon polymerization. The phosphorylated from of actin showed no polymerizing activity, while the unphosphorylated form possessed the ability to polymerize into F-actin. These results suggest that phosphorylation of Physarum actin is involved in reorganization and/or preservation of the actin molecules in the process of sclerotium formation.
Furuhashi
K
K
Department of Biology, Faculty of Education, Shiga University, Japan. furuhasi@sue.shiga-u.ac.jp
Ishigami
M
M
Suzuki
M
M
Titani
K
K
D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D015180:Electrophoresis, Gel, Two-Dimensional; D013058:Mass Spectrometry; D008854:Microscopy, Electron; D010748:Phosphopeptides / Q000032:analysis; D010766:Phosphorylation; D010769:Phosphothreonine / Q000032:analysis; D016839:Physarum polycephalum / Q000378:metabolism*; D014867:Water / Q000378:metabolism
D000199:Actins; D010748:Phosphopeptides; D014867:Water; D010769:Phosphothreonine; D000469:Alkaline Phosphatase